Process of minimizing foam production in steam generation



Patented Nov. 13, 1951 OFFICE PROCESS OF MINIMIZING FOAM PRODUC- TION IN STEAM GENERATION Arthur L. Jacoby, Western Springs, and Clarence J acklin,

Downers Grove,

111., assignors to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application August 3, 1948, Serial No. 42,344

13 Claims. (01. 252-321) The present invention relates to improved antifoaming compositions which are added to water that is subjected to boiling, as in the boilers of locomotives, stationary steam generators, evaporators, and in other instances wherethe boiling of water occurs, especially under superatmospheric temperature and pressure conditions, whereby the tendency of the water therein to foam is prevented or reduced and the boiling characteristics of the water so improved that priming of the steam generator and carryover of boiler water with the steam therefrom is prevented.

It is well known that in the operation of steam boilers, such as in railroad locomotives, in electric power plants and the like, or in other boiling operations where steam is formed, as for example in evaporators, that the water therein, even though initially it shows little tendency to foam, will, when the amount of total dissolved solids approaches a relatively high concentration due to the production of steam, develop a very decided tendency to foam. This foaming of the water in a boiler producing steam is characterized not only by an accumulation of relatively stable froth or foam on the surface of the boiler water but also by the formation at the heat transfer surfaces in the boiler of extremely small steam bubbles. These minute bubbles show almost no tendency to coalesce and the result is that the entire volume of water in the steam generator is lifted in the form of so-called light water, which is actually an intimate mixture of boiler water and tiny steam bubbles. When this occurs, considerable quantities of boiler water are physically carried out of the boilers or evaporators with the steam, thereby introducing solid matter into the steam lines and into the eventual condensate. Such carryover has many disadvantages because it tends to contaminate and restrict the steam lines, to plug or corrode the valves, to deposit on turbine blades, to plug and cause burning out of superheater tubes, and under serious conditions may even impair the cylinders and piston rods of steam engines or otherwise render the steam unfit for use. The carryover is frequently due in part, at least, to priming, or what may be described as surging or boilingover of the water.

Attempts have been made in the past to control foaming and priming by controlling the dissolved solids content of the water as by excessive blow-down of the boilers, that is, the removal, either continuously or periodically, of a portion of the boiler water containing the undesired excess solids. Also, it has been common to add materials for the purpose of abating the foam as by the injection of such materials as castor oil, tallow, and the like. While these fatty materials, notably castor oil, have some small degree of efllciency, they are, on the other hand, quite deficient in that they introduce new difllculties which, in some instances, are worse than the conditions they are intended to cure. In the first place, these fatty materials or glycerides are very unstable under severe hydrolytic conditions encountered in steam generation, particularly under the conditions of superatmospheric pressure, the corresponding high temperatures and the alkalinity of the boiler water. The resultant decomposition products which remain in the boiler tend to increase the foaming tendencies of the boiler water and to accumulate in such a way as to give a compound dirty boiler, necessitating frequent washing. Furthermore, in many instances certain of the decomposition products thus produced, or sometimes even the materials themselves, have a definite volatility with steam and will, therefore, steam-distil out of the steam generators, thus appearing in the steam and in the eventual condensate. This, of course, is also undesirable. Additionally, such types of antifoaming agents usually are of such a low order of efilciency that they have to be employed in relatively large quantities, adding not only to the expense but also to the inconvenience of operating the steam generators; and since they are so unstable their effectiveness is of short duration,

' necessitating the continual charging into the boilers or other steam generators of relatively large amounts of these older antifoaming agents.

The most noteworthy advance over the use of the fatty glycerides described above was the discovery and development of certain high molecular weight substituted polyamides, which antifoaming compounds overcame many of the disadvantages of the former, especially in that they were highly eflicient at lower dosage levels and much more resistant to decomposition, so that their effective life was relatively greater.

One of the objects of this invention i to provide a new and improved process for preventing the foaming and priming of steam generators, thus improving the quality of the steam produced thereby.

Another object is to provide new and improved compositions for adding to the water in a steam generator to prevent or reduce its tendency to foam.

Another object is to provide antifoaming compositions which are effective to prevent foaming when used in very low dosages.

A further object is to provide highly effective antifoam compositions which are readily and easily dispersible when added to the feed water entering a steam generator.

Another object of this invention is to provide antifoam compositions in which the active effective ingredients are readily soluble in water at relatively low temperatures, (e. g. 'lfi'degrees F.) but decrease in solubility when the water is heated to relatively high temperatures such as are employed in the generation of steam under superatmospheric pressures and the corresponding temperatures.

Still another object of the invention is to provide a process of generating steam and new and improved antifoam compositions therefor wherein the period 'of effectiveness of the antifoam composition is greatly prolonged as compared to the period of efiectivenes of other antifoam compositions presently known in the art.

Still another object of the invention is to provide a new and improved process of inhibiting foaming during steam generation which permits operations at higher dissolved solids contents than has heretofore been, considered possible.

An additional object is to provide new and useful antifoaming compositions of an extremely high order of resistance to decomposition under the conditions prevailing in steam generation. Other objects will appear hereinafter.

.In accordance with this invention, it has now been discovered that there is a series of compounds, which may be broadly designated as high molecular weight polyoxyalkylene glycols,

that are very effective when used as antifoaming and antipriming agents in steam generators. These glycols possess several important advantages over formerly known antifoam composi-- tions. They are all much more efiective than any of the fatty glycerides, and many are more effective than. any hitherto known materials. Furthermore they are much more stable to decomposition under conditions of use than any of the glycerides or polyamides, thus giving them a greatly prolonged period of effectiveness in preventing foaming. In general, they are more readily dispersed in the water being fed to the steam generator than are older materials, and a further advantage offered by many of these polyoxyalkylene glycols is that they are liquids or very low-melting waxy materials which are readily soluble at ordinary temperatures.

The preferred polyoxyalkylene glycols employed in the practice of this invention may be represented by the structural formula H (OCnHzn) 10H wherein n is 2 or 3 or may have both values, and a: is an integer of approximately 20 or larger. Such compounds are thus seen to include polyoxyethylene glycols, polyoxypropylene glycols, and polyoxyalkylene glycols in which the alkylene groups includ both ethylene and propylene in any proportion and in a random or irregular sequence, with respect to each other, in the polyoxyalkylene chain.

In order that these polyoxyalkylene glycols possess the property of efliciently preventing the foaming and priming of steam generators, they should be of relatively high molecular weight and, while the lower limiting value of molecular weight will vary somewhat with the ratio of ethylene to propylene groups in the polyoxyalkylene chain it will, in general, be in the neighborhood of approximately 6000 when the glycol is a polyoxyethylene glycol, and 1000 when the glycol is a polyoxypropylene glycol. When the alkylene groups in the polyoxyalkylene chain consist of both ethylene and propylene, the lower limiting value of molecular weight will be intermediate between 1000 and 6000.

Generally stated, therefore, it may be said that the polyoxyalkylene glycols employed for the purpose of this invention may be characterized as having a molecular weight of at least 1000. The foam inhibiting compounds employed for the purpose of the invention may also be described as being non-ionic in that they do not contain ionizable groups such as carboxy or sulfonic groups.

The polyoxyalkylene glycols of this invention are already well known and the various means of preparing them are well understood by those skilled in the art. Reference may be made to an article by McClelland and Bateman, entitled Technology of the Polyethylene Glycols and Carbowax Compounds, which appeared on pages 247-251 of the February 10, 1945, issue of Chemical and Engineering News for preparation oi. the polyoxyethylene glycols. The preparation of polyoxyalkylene glycols is also described in United States Patent 1,921,378 and the preparation of polyoxyalkylene glycols containing both.

ethylene and propylene groups is described in United States Patent 2,425,845.

Specific examples of polyoxyalkylene glycols suitable for the practice of this invention include (1) Carbowax 6000, which is a commercial grade of polyoxyethylene glycol of average molecular weight 6000 to 7500 with a freezing point (F. P.) of 58-62 degrees C. and a viscosity at 210 degrees F. of 6000 to 7500 Saybolt seconds (S. U. S.); (2) UCON" fluid 75H-63,000 which is a polyoxyalkylene glycol containing ethylene oxide and propylene oxide in the polyoxyalkylene chain in a weight ratio of approximately 3 1 and having a viscosity at degrees F. of approximately 63,000 S. U. S.; (3) UCON fluid 75-H-3000 which is a polyoxyalkylene glycol containing ethylene oxide and propylene oxide in the polyoxyalkylene chain in a weight ratio of approximately 3:1, having a viscosity at 100v degrees F. of approximately 3000 S. U. S., and having a molecular weight of approximately 7000; and (4) polyoxypropylene glycols of average approximate molecular weights of 1000, 1200, 2000,-and 3000, respectively.

The products hereinabove described may be liquids or low-melting wax-like solids, and may be entirely soluble in cold water or only partially soluble. In the latter case, they are relatively easily dispersed in the feed water by means of additional dispersing agents, as described below. All of the products exhibit substantial insolubility in hot water,' the phenomenon of decreasing solubility in water with increasing temperature being characteristic of compounds of this class which contain multiple ether linkages and in which the ratio of ether linkages to carbon is sufiiciently great to permit the weak hydrogen bonding effect of the ether oxygen to confer water solubility.

The amounts of an antifoam agent employed in inhibiting the foaming of water in a steam generator will depend upon several factors, among them the per cent of solids in the foaming liquid, the nature of the solids, the alkalinity, temperature, and pressure, the type and degree of circulation in the steam generator, the rate of steam production, and the amount of foamsuppression desired. It is, therefore, impossible to state any rigid rules for estimating the amount of an antifoam which needs to be used. The amounts of the polyoxyalkylene glycols of this invention which are required, are, however, extremely small. For many purposes, amounts of the order of 0.01 grain per gallon to 0.02 grain per gallon in the feed water are sufficient, and under certain conditions quantities as low as 0.001 grain per gallon in the feed water have proved efiective. In general, it can be said that quantities greater than 0.1 grain per gallon in the feed water would seldom be required.

By way of illustrating the remarkable eifectiveness of the polyoxyalkylene glycols of this invention, the method of testing their antifoam eiiiciency in the laboratory will be described and exemplary data given. I

In the laboratory, the experimental boiler used was of the type described in the publication Solid Matter in Boiler Water Foaming, by Foulk and Brill, which appeared in the periodical Industrial and Engineering Chemistry, volume 27, pages 1430-35. This boiler was fitted with sight glasses on each side of the steam release space so that conditions in the boiler in a zone several inches above and below the normal water level were observed while the boiler'was operating under pressure. It was also equipped with an automatic water level control which held the water level within a range of :0.25 inch.

In the series of experiments described below, a feed water was used having the following composition, expressed in parts per million, by weight:

Calcium hardness (as CaCOa) 154.0 Magnesium hardness (as CaCOa) 154.0 Alkalinity (methyl orange) (as CaCOs) 726.0 Sodium chloride (as NaCl) 85.5 Sodium sulfate (as Na2SO4) 718.0

Tannin extract, dry 34.2

To this feed water was added the antifoam composition of the character and in the quantity specified in the specific experiment, and this water was then gradually concentrated in the test boiler by evaporation at the rate of six gallons per hour at 250 pounds per square inch (p. s. i.) gauge pressure. A continual recording was made of the relative conductivity of the condensate from the boiler, and continual observations were made of the character of the boiling and the amount of foaming as seen through the sight glasses. When the antifoam thus introduced continuously with the feed water was no longer able to overcome the foaming tendencies brought about by the concentration of dissolved solids in the boiler water, the foam height became great enough to cause boiler water to be carried out of the boiler with the steam, and this end-point of the test was determined both by observation through the sight glasses, and, particularly, by the abrupt increase in the conductivity of the steam, as shown in the continuous recorder. At this end-point, a sample of the boiler water was withdrawn from the boiler and analyzed, and the effectiveness of the antifoam expressed in terms of the total dissolved solids concentration which it permitted the boiler to carry.' A high value of total dissolved solids ('IDS) indicates an effective antifoam. With no antifoam, this feed water gives a carryover at a total dissolved solids value of approximately 175 grains per gallon.

Test I The material tested as an antifoam in this experiment was Carbowax 6000, which has been particularly described hereinabove. The material was completely soluble in the feed water at room temperature, and was proportioned to the feed water in the form of an aqueous solution in quantity sufllcient to give a concentration of the polyoxyethylene glycol in the feed water of 0.0855 part per million by weight without appreciable dilution of the feed water. Carryover did not occur until the total dissolved solids in the boiler water had reached 1757 grains per gallon.

Test II A polyoxypropylene glycol of average molecular weight of approximately 1200 was incorporated into a dry, powdered formulation as follows: Three grams of the glycol was mixed with one gram of dipropylene glycol and one gram of oleic acid. The resulting liquid mixture was intimately mixed, by grinding, with g. of a dry, pulverized lignin derivative commonly used in boiler water treatment, and made by desulfonation and partial depolymerization' of sodium lignin sulfonate by treatment with aqueous alkali at high temperatures. This material exhibits an excellent dispersing eiTect on the polyoxypropylene glycol but exerts no antifoam effect per se. The resulting dry-appearing pulverized composition, containing three parts by weight of the glycol, was added to the feed water at a dosage of 8.55 parts per million (P. P. M.), resulting in a concentration of the glycol of 0.257 P. P. M. in the feed Water. This permitted a total dissolved solids concentration in the boiler of 562 grains per gallon before carryover occured.

Test III UCON fluid 75-H-63,000, which has been particularly described hereinabove, was dissolved in the feed water at a dosage of 0.0427 P. P. M. It permitted a concentration of total dissolved solids in the boiler water of 1257 grains per gallon before carryover occurred.

Test IV UCON fluid 75-H-3000, which has been particularly described hereinabove, was dissolved in ethanol at a concentration of 64.8 milligrams per milliliters of solution. Sufficient of the ethanol solution was added to the feed water so as to give a concentration of the polyoxyalkylene glycol in the feed water of 0.0855 P. P. M. by weight. This permitted a total dissolved solids concentration in the boiler water of 466 grains per gallon before carryover occurred.

Test V A polyoxypropylene glycol of average molecular weight of approximately 2000 was intimately mixed, by grinding, with the desulfonated lignin derivative described in Test II in the proportion of 3 parts, by weight, of the glycol to 97 parts of the lignin derivative. The resulting dry-appearing powdered composition was readily dispersible in the feed water to yield a stable dispersion. It was employed in a concentration of 4.27 P. P. M. in the feed water, giving a concentration of the polyoxypropylene glycol in the feed water of 0.128 P. P. M. by weight. This permitted a total dissolved solids concentration in the boiler water of 2681 grains per gallon before carryover occurred.

Test VI A polyoxypropylene glycol of average molecular weight of approximately 3000 was incorporated into a dry, powdered composition in the same manner. and proportions, as described under Test V. The resulting readily water-dispersible composition was added to the feed water at a dosage of 2.84 P. P. M., resulting in a concentration of the polyoxypropylene glycol in the feed water of 0.0855 F. P. M. by weight. This permitted a total dissolved solids concentration in the boiler water of approximately 2000 grains per gallon before carryover occurred.

One of the difliculties of using most antifoam materials is that of conveniently introducing them into the water in small, controlled amounts so that their maximum effectiveness is utilized. While many of the polyoxyalkylene glycols employed in accordance with this invention are readily soluble in cold water, others are not completely soluble and must be rendered readily dispersible for use. Liquids, waxes, and preformed emulsions are inconvenient to apply to the feed waters used by locomotives and other power plants. It is thus a further object of this invention to provide the polyoxyalkylene glycols compounded with other water treating chemicals in a powdered or briquetted form which can readily and conveniently be added to water, and which will disperse in the water quickly without excessive agitation or mixing.

The polyoxyalkylene glycols employed in the practice of this invention can all be incorporated into dry powdered materials such as powdered tannin, sodium lignin sulfonate, the desulfonated lignin described in Test II hereinabove, soda ash, various orthophosphates and polyphosphates. Depending somewhat upon the powdered absorbent selected, amounts of the polyoxyalkylene glycols of the order of to 10% of the total composition may be readily incorporated to give a dryappearing pulverized product.. By the use of suitable binders and other well-known techniques, such compositions may also be briquetted.

The resulting dry-appearing products just described are readily and completely dispersible in water when the polyoxyalkylene glycols themselves are soluble or dispersible. When polyoxyalkylene glycols are employed which are substantially insoluble in water, such as, for example, the products described in Tests II, V and VI, these, too, give dry-appearing compositions by the method described if a dispersing agent is used in conjunction with them. In fact, many of the common water treating chemicals of a tannin or ligm'n nature behave as sufiiciently powerful dispersants to readily disperse the insoluble polyoxyalkylene glycols in the form of a relatively stable aqueous dispersion. Where it is not desired to use the tannins or lignin derivatives in quantity sufficient to act as dispersants for the polyoxyalkylene glycols, a small amount of soap, such as the alkali metal soaps of oleic acid or tall oil, or a sulfonated oil, may be employed with good results, and the amount of soap or sulfonate thus required is insuflicient to interfere with the powerful antifoam effect of the polyoxyalkylene glycols or to render the boiler "compound dirty.

In general, then, the polyoxyalkylene glycols of this invention may be prepared in the form of dry-appearing pulverized or briquetted compositions which are readily and completely dispersible in water with a minimum of agitation by incorporating them, with or without a dispersant such as soap or sulfonated oil, with various tannins.

range. In locomotive boilers, steam is generally generated at pressures around 250 pounds per square inch and the corresponding temperatures. Excellent results have been obtained .with the practice of the invention at pressures within the range of to 300 pounds per square inch and the corresponding temperatures. The invention can also be used, however, in connection with the generation of steam at much higher pressures and the corresponding temperatures, as, for example, in stationary boilers operating at pressures as high as 1000 to 1500 pounds per square inch. The compositions employed in accordance with the invention are effective not only in inhibiting foaming but also in conditioning and improving the quality of the steam. For this purpose, they may be used in even smaller amounts than the amounts required for the complete in-- hibition of foaming and priming.

The polyoxyalkylene glycols employed in the practice of this invention are desirably used in conjunction with other organic water treating chemicals of the tannin and lignin types in treating many water supplies as will be seen from the following. On waters high in magnesium salts in which the magnesium in the boiler will generally be in the form of magnesium hydroxide, it is desirable that suillcient of hydroxylated organic material suchas tannins, tannic acid, gallic acid, pyrogallol, catechol, phloroglucinol, etc. be added along with the polyoxyalkylene glycols. These hydroxylated organic compounds have the ability of nullifying the bad effects of the magnesium hydroxide. Magnesium hydroxide appears to partially selectively adsorb the antifoam material and so take it out of the boiler water so that the full antifoam action cannot be exerted by the antifoam compositions when in this adsorbed state. However, when an organic material such as a tannin is added, magnesium hydroxide appears to lose its ability to interfere with the antifoam action. Inasmuch as most boiler feed waters encountered will have varying amounts of magnesium salts present, it is desirable that such hydroxylated organic compounds be mixed with the polyoxyalkylene glycols prior to addition to the boiler feed water.

Thus another advantage is evident in preparing and using the pulverized or briquetted compositions hereinabove described containing both the polyoxyalkylene glycol antifoam and the polyhydroxylated organic material of the tannin or lignin-derivative type.

As will be apparent from the foregoing description, the compounds employed in accordance with the invention do not all give the same results and from that standpoint are not necessarily equivalents. Some of these polyoxyalkylene glycol compositions, especially those of the type referred to in Test VI, are truly remarkable in their foam inhibiting properties and chemical stability even when compared with the best of the antifoam compositions which have been preter therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene, and mixtures thereof, the average molecular weight of said polyoxyalkylene glycol being at least about 1000 when the polyoxyalkylene glycol is a polyoxypropylene glycol, at least approximately 6000 when the polyoxyalkylene glycol is a polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being suflicient to substantially inhibit foaming and priming.

2. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene, and mixtures thereof, and the average molecular weight is within the range of 1000 to 7500, the average molecular weight of said polyoxyalkylene glycol being at least 1000 where the polyoxyalkylene glycol consists of polyoxypropylene glycol, at least 6000 where the polyoxyalkylene glycol consists of polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxya kylene glycol contains both oxyethylene and oxypropylene groups, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being suflicient to substantially inhibit foaming and priming.

3. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure condi-.- tions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol containing ethylene oxide and propylene oxide in a weight ratio of approximately 3:1 and an average molecular weight of approximately 7000, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being sumcient to substantially inhibit foaming and priming.

4. A process of minimizing the production of foam in and priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyethylene glycol having an average mclecular weight of 6000 to 7500, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being sufficient to substantially inhibit foaming and priming.

5. A process of minimizing the production of foam in and priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxypropylene glycol having a molecular weight within the range of 1000 to 3000, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being suflicient to substantially inhibit foaming and priming.

6. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene, and mixtures thereof, the average molecular weight of said polyoxyalkylene glycol being at least about 1000 when the po yoxyalkylene glycol is a polyoxypropylene glycol, at least approximately 6000 when the polyoxyalkylene glycol is a polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being within the range of 0.001 grain to 0.1 grain per gallon of water.

7. A process of minimizing the production of foam in and priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene, and mixtures thereof. the average mo ecular weight of said polyoxyalkylene glycol being at least about 1000 when the polyoxyalkylene glycol is a polyoxypropylene glycol, at least approximately 6000 when the polyoxyalkylene glycol is a polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions, said quantity being within the range of 0.001 grain to 0.1 grain per gallon of water, and said superatmospheric wassure conditions being within the range of ICU to 1500 pounds per square inch and the corresponding temperatures.

8. A process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amoun of total solids tending to produce foaming and priming a quantity of a polyoxyalkylene glycol, wherein the alkylene radicals are selected from the group consisting of ethylene, propylene, and mixtures thereof, the average molecular weight of said polyoxyalkylene glycol being at least about 1000 when the polyoxyalkylene glycol is a polyoxypropylene glycol, at least approximately 6000 when the polyoxyalkylene glycol is a polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and'oxypropylene groups, said polyoxyalkylene lycol being substantially insoluble in said water under said steam generating conditions, said quantity being within the range of 0.001 grain to 0.1 grain per gallon of water, and said superatmopheric pressure conditions being within the range of 100 to 300 pounds per square inch an the corresponding temperatures.

9. The process of minimizing the production of a foam in steam boilers during steam generation which comprisesincorporating in a water therein containing an amount of total solids tending to produce foaming a quantity of a polyoxyalkylene glycol wherein the alkylene radicals are both ethylene and propylene and the average molecular weight is at least 1000, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being sufficient to substantially inhibit average molecular weight of said product is at least 1000, said polyoxyalkylene glycol being substantially insoluble in said water under said steam generating conditions and said quantity being sufficient to substantially inhibit said foaming.

11. The method of generating steam from a boiler water having a tendency to foam on boiling and which contains magnesium compounds which comprises dispersing in said water a quantity of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, the average molecular weight of said polyoxyalkylene glycol being at least about 1000 where the polyoxyalkylene glycol consists of polyoxypropylene glycol, at least 6000 where the polyoxyalkylene glycol consists of polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups and said polyoxyalkylene glycol being substantially insoluble in said boiler water under the steam generating conditions, and a quantity of a hydroxylated organic compound from the group consisting of tannins, sodium lignin sulfonate and desulfonated lignins effective to nullify the action of the magnesium compounds on said polyoxyalkylene glycol, the quantity of the polyoxyalkylene glycol being effective to inhibit the tendency of said water to foam on boiling, and heating the resultant aqueous dispersion to the boiling point.

12. A liquid for the generation of steam comprising water containing magnesium compounds, an amount of total dissolved solids tending to 12 produce foaming and priming when heated to the boiling point, a quantity of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, said polyoxyalkylene glycol is substantially insoluble in said boiler water under the steam generating conditions, and the average molecular weight is at least 1000 where the polyoxyalkylene glycol consists of polyoxypropylene glycol, at least 6000 where the polyoxyalkylene glycol consists of polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups, the aforesaid quantity being effective to inhibit thetendency of said water to foam on boiling, and a quantity of a hydroxylated organic compound from the group consisting of tannins, sodium lignin sulfonate and desulfonated lignins effective to nullify the action of the magnesium compounds on said polyoxyalkylene glycol.

13. An antifoam composition for minimizing the production of foam in the generation of steam from water containing magnesium compounds which comprises essentially a quantity of a polyoxyalkylene glycol wherein the alkylene radicals are selected from the group consisting of ethylene, propylene and mixtures thereof, said polyoxyalkylene glycol is substantially insoluble in said water under the conditions of steam generation, and the average molecular weight is at least about 1000 where the polyoxyalkylene glycol consists of polyoxypropylene glycol, at least 6000 where the polyoxyalkylene glycol consists of polyoxyethylene glycol and a minimum average molecular weight between 1000 and 6000 when the polyoxyalkylene glycol contains both oxyethylene and oxypropylene groups, the aforesaid quantity being efiective to inhibit the tendency of said water to foam on boiling, and a quantity of a hydroxylated organic compound from the group consisting of tannins, sodium lignin sulfonate and desulfonated lignins effective to nullify the action of said magnesium compounds on said polyoxyalkylene glycol when said composition is dispersed in water containing magnesium compounds.

ARTHUR L. JACOBY.

CLARENCE JACKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Tremain et al. Nov. 9, 1938 OTHER REFERENCES Number 

1. A PROCESS OF MINIMIZING THE PRODUCTION OF FOAM IN AND PRIMING OF STEAM GENERATORS OPERATING UNDER SUPERATMOSPHERIC PRESSURE CONDITIONS WHICH COMPRISES INCORPORATING WITH A WATER THEREIN CONTAINING AN AMOUNT OF TOTAL SOLIDS TENDING TO PRODUCE FOAMING AND PRIMING A QUANTITY OF A POLYOXYALKYLENE GLYCOL, WHEREIN THE ALKYLENE RADICALS ARE SELECTED FROM THE GROUP CONSISTING OF ETHYLENE, PROPYLENE, AND MIXTURES THEREOF, THE AVERAGE MOLECULAR WEIGHT OF SAID POLYOXYALKYLENE GLYCOL BEING AT LEAST ABOUT 1000 WHEN THE POLYOXYALKYLENE GLYCOL IS A POLYOXYPROPYLENE GLYCOL, AT LEAST APPROXIMATELT 6000 WHEN THE POLYOXYLKYLENE GLYCOL IS A POLYOXYETHYLENE GLYCOL AND A MINIMUM AVERAGE MOLECULAR WEIGHT BETWEEN 1000 AND 6000 WHEN THE POLYOXYALKYLENE GLYCOL CONTAINS BOTH OXYETHYLENE AND OXYPROPYLENE GROUPS, SAID POLYOXYALKYLENE GLYCOL BEING SUBSTANTIALLY INSOLUBLE IN SAID WATER UNDER SAID STEAM GENERATING CONDITIONS AND SAID QUANTITY BEING SUFFICIENT TO SUBSTANTIALLY INHIBIT FOAMING AND PRIMING. 